Strangeness production in heavy-ion collisions

Strangeness production is a very useful diagnostic tool in finding the quar k-gluon plasma. We review its uses in understanding relativistic heavy-ion collisions. A brief introduction to the main theoretical tools used in inte rpreting strangeness production is given, and the experimental methods used to extract the signals are discussed in detail. The experimental results f rom the Brookhaven AGS and CERN SPS programs are presented. We discuss the interpretation of these results, emphasizing their role in the discovery of deconfined quark matter at CERN. Future experiments at RHIC and at the CER N LHC are described.